A derrick structure which was developed in 1987 by the present inventor and which has shown great promise embodies the RamRig.TM. concept. Two hydraulic piston-cylinder arrangements are used in the derrick for raising and lowering the drill string. The cylinders operate between the drill floor and a yoke which travels on guide rails in the derrick itself The advantages of this concept are numerous, some of the most important being that it is possible to place the drill floor at a higher level than the platform floor, that a derrick may be constructed having a significantly lower air resistance, that a higher level of safety and longer lifetime are attained for the most expensive components of the derrick.
Since it is possible to position the drill floor higher than the platform floor, pipe handling is significantly simplified. There is no longer any need to arrange the pipe handling equipment at a high level in the derrick. All pipe handling equipment may be placed on the platform floor and the drill floor.
The object of the present invention is to solve important, practical problems in the realization of the RamRig.TM. concept.